1. Field of the Invention
The present invention relates to a cap separable from bottle at the time of disposal. More specifically, the invention relates to a cap that is strongly fitted and secured to the mouth of a container but that can be easily removed from the mouth of the container without using any special tool, and that offers excellent sealing and tamper-evidence.
2. Description of the Prior Art
Plastic caps have an excellent moldability, exhibit excellent flexibility and can, hence, be strongly fitted and secured to the mouths of containers by the capping operation to maintain high degree of sealing.
In many cases, however, the plastic caps are used for a glass bottle or the plastic containers made of materials different from the cap materials. To meet the demands for reusing the resources and for separating the cap from the bottle at the time of disposal, it has been desired to easily remove the caps from the mouths of the containers without using a tool such as cutter or the like.
There have been proposed a variety of caps separable from bottle at the time of disposal. For example, Japanese Utility Model Laid-Open No. 59247/1994 discloses a container closure comprising a cap body fitted and secured to the mouth of a container, a cylinder screwed to the cap body, and an overcap coupled by hinges to the cylinder. In the container closure, the cap body comprises a top plate portion having a breaking portion for forming a flow-out port, a side wall coupled integrally to the peripheral edge of the top plate, and an inner ring that downwardly extends from the inner surface of the top plate portion maintaining a suitable gap from the side wall. That is, the cap body is secured to the mouth of the container as the mouth of the container is fitted to between the side wall and the inner ring. Besides, the side wall is formed being broadened toward the back thereof or has a plurality of slits formed maintaining a suitable distance in the circumferential direction and extending in the direction of height, so that the cap body can be removed from the mouth of the container without using any special tool. Furthermore, a screw thread is formed on the upper outer peripheral surface of the side wall to hold the cylinder. When the cylinder is engaged with, and held by, the side wall, the side wall is pushed by the cylinder and is firmly held by the mouth of the container to maintain good sealing.
According to the container closure of the above prior art, the cylinder formed integrally with the overcap is turned, so that the cap body is removed from the side wall. Thus, the cap body can be easily removed by hand from the mouth of the container and can, hence, beseparated easily from the container at the time of disposal. However, this container closure does not offer tamper-evidence. That is, the container closure is removed by breaking neither the cylinder formed integrally with the cap nor the cap body. Therefore, even if the container closure that was once removed from the mouth of the container is fitted again to the mouth of the container, this fact cannot at all be recognized by a third person.
In order to produce the above-mentioned container closure, furthermore, the cylinder formed integrally with the overcap and the cap body must be formed respectively, and the two must then be combined together, leaving a problem of low productivity.
Furthermore, Japanese Utility Model Laid-Open No. 9751/1995 discloses a container closure comprising an inner plug fitted and secured to the mouth of the container, an outer cylinder and an overcap. Like the cap body mentioned above, the inner plug of the container closure has, formed in the top plate portion thereof, a breaking portion for forming a flow-out port, and permits the mouth of the container to be fitted between the side wall and the inner ring. Moreover, the top plate portion has an annular erected portion that is so formed as to surround the breaking portion, and the overcap is fitted being screwed about the outer surface of the erected portion. The outer cylinder is so provided as to surround the outer peripheral surface of the side wall of the inner plug, the outer cylinder and the side wall of the inner plug are formed integrally via a weakened portion, and a reinforcing ring is fitted in space between the inner surface of the outer cylinder and the outer surface of the side wall. That is, in a state where the container closure is fitted to the mouth of the container, the side wall of the inner plug is pushed onto the wall of the mouth of the container by the reinforcing ring, whereby the inner plug is firmly secured to the mouth of the container to maintain good sealing. The outer cylinder can be easily torn away from the inner plug by breaking the weakened portion. With the outer cylinder being torn away from the inner plug, the side wall is no longer pushed by the reinforcing ring. Therefore, the inner plug can be removed from the mouth of the container without using any special tool. As described above, this container closure can be separated easily from the container at the time of disposal. Besides, the container closure offers tamper-evidence since the inner plug is removed from the mouth of the container after the outer cylinder is turn away from the inner plug.
According to the container closure of the above-mentioned Japanese Utility Model Laid-Open No. 9751/1995, however, the side wall is pushed to the wall of the mouth of the container by the reinforcing ring. It is therefore necessary to form a thin portion in the side wall so that the side wall can be easily deflected. Therefore, the thin portion of the side wall is often broken when the inner plug is capped to the mouth of the container. Besides, the container closure has a triple-wall structure consisting of inner ring, side wall and outer cylinder. In addition, the reinforcing ring must be fitted between the side wall and the outer cylinder. Accordingly, the container closure is not easily molded, and there remains a problem that the reinforcing ring falls down prior to effecting the capping operation.